1. Field of the Invention
The present invention relates to a message transfer system and method. More particularly, it relates, in a system wherein a message longer than a packet length is segmented and sent, and the message is reassembled on a receiving side, thereby to transfer the message, to a transfer system and method well suited to communication facilities which simply control communications with the smallest buffer capacity corresponding to a message processing ability.
2. Description of the Prior Art
Heretofore, some of network systems etc. based on loop transmission have adopted a message transfer method wherein a message longer than a packet length is segmented and sent from a node, and the message is reassembled on a receiving side, thereby to transfer the message. For the purpose of making it possible to receive packets from all nodes and to reassemble messages, this method has employed a scheme in which message buffers for individual senders are prepared in correspondence with the maximum node number and are installed in each of the nodes.
As examples of pertinent literatures, there are mentioned "DATA TRANSMISSION" (Nippon telegraph and Telephone corporation), p. 354-p. 367, and "PACKET SWITCHING TECHNOLOGY AND ITS APPLICATION" (p. 88-p. 92, 1982) edited by the Japan Institute of Electronics, Information and Communication Engineers.
With the prior art, since nodes having acquired fields send packets without any limitation, packets from different nodes coexistingly arrive at a certain node in some cases. On the receiving side, therefore, the buffers for gathering the packets and reassembling messages for the individual sender nodes need to be prepared in the largest number (usually, 32-128) of nodes connected to a loop. The rate of concentration of messages per node, however, is not always equally high for all the nodes though it depends also upon the way of application of the message transfer system. In a case where the rates of concentration are somewhat nonuniform, the rates of usage of most buffers will become much lower than the rate of usage of a buffer for a specified node, and the number of buffers simultaneously used will become small as compared with the total number of the nodes. Accordingly, the prior art has the problem of wastefulness in that the large quantities of buffers must be prepared irrespective of the utilization factors of the buffers and the number of the buffers simultaneously required.